We built it inside the account you already use — no third-party escrow, no cross-chat negotiation. You'll find it on the Shop page: open the Marketplace tab — the second one, right after Store — marked with a BETA badge.
Browsing it is simple: a feed of ASIC listing cards, each showing the machine's specs, the price the seller set, its status (online, offline, needs repair), and a Buy button. Buy a card, and that capacity lands on your account. What you're looking at is a market in its first days — which, if you're early, is exactly the point (more on that below).